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Topic: 1971 GTR 350 Not Shifting (Read 377 times)

Howdy, Finally got my bridgestone running the other day only to find that the bike shifted into first but then wouldn't shift back into neutral or into second gear. I disabled the entire engine and didn't seem to find much. However, I stumbled across one of my shifting forks with some serious wear around second gear where the gear had been hitting/wearing on the fork. Is this common, what could cause this, and could this possibly be the answer to my issue of shifting. Any help is appreciated. Below are two pictures, one with an unworn fork and where it is hitting on the gear, and another photo where the fork that I believe was in that position was worn. I have a feeling that when I reassembled the engine previously that I maybe put a different fork that was unworn in the position where the work fork used to be, but that still would not explain why the shifter drum wouldn't not spin inside the cases. Either way I would like to get this issue straightened out so I don't have to disassemble the motor a 10th time lol. Regards

You can put the assembled transmission in the bottom half of the case along with the shift drum and forks, then slowly spin the drum while watching the gears engage/disengage. It may be necessary to spin the gear shafts a little to get dogs to line up as the gears move. Any binding or misalignment should be visible.

Bridgestone didn't get everything quite right, the shift fork/second gear interference you have found is not unusual. The engine I'm currently rebuilding has it. Not helped by a bit of wobble on the second gear pinion. Suggest you file some clearance in the web or maybe reshim the gear to move it over. ( Fork blueing was also a common issue on early gearboxes due to inaccurate factory shimming of the gears). This is probably not the cause of the shift problem.

The drum guide bolt (bottom of crankcase) can jam the box if it's aluminium washer is missing or flattened. More likely is an issue with the ratchet pawls on the end of the shifter drum. Check the springs are not squashed and the pawls are installed the right way up, see manual for guidance. Most likely cause is the over-run stopper plate (item 12 on gear change page, Parts Manual) being installed 180 degs out of position, very easily done, it has an odd number of teeth 7. See Figs 34 & 35 in the engine rebuild section of the Service Manual, with the change mechanism centered at rest a single tooth(marked C3 on drawing) should point toward the centre of the change arm. Drawing shows the flats on the shift drum in a vertical position, this corresponds to the box being in third gear but it is not essential to have the box in third before installing the stopper plate because it self centres after each gear change. As long as it centres on a single tooth it will be correct. Put it in 180 degs out and the box won't change !! Hope you can follow this.

As Karl Swartout says above, carefully put it back together, checking at each stage that everything is free and you can shift through all the gears, particularly before bolting the cases up and it will be fine. Brian.

An after thought, (was sometimes called 'Columbo' at work ) you have obviously identified the correct fork for the 1st/2nd gear. You should find one of the other forks has rather crude grooves ground into the tip of the longer fork end. This is the 5th/6th gear fork and was a factory mod to improve oil supply and reduce blueing of the tip. That ensures all the forks are replaced as factory assembled.

You should find one of the other forks has rather crude grooves ground into the tip of the longer fork end. This is the 5th/6th gear fork and was a factory mod to improve oil supply and reduce blueing of the tip. That ensures all the forks are replaced as factory assembled.

Brian, is this documented somewhere or is it your personal observation? Didn't see anything in the service letters about this, but it's possible I may not have that one if it's in there.

Hi Mike, Fork groove mod was detailed in a BS Service Bulletin dated August 67 and was effective from No. 21S01001. Was intended to prevent fork scoring (blueing?) when in 5th gear. Not sure where I came across the bulletin, may have come with one of the bikes. We lost access to a number of BS service bulletins and Rockford service letters when Ray Oliver closed his Redimport web site. Would be nice if they could be transfered to this forum. Brian.

Mike, I assume the number series above refers to the 'Rockford service letters'

The shift fork document is a 'Bridgestone Service Bulletin, which I guess were factory issued. Unfortunately, it has been printed or copied off centre and it's number has been chopped off. Never noticed before but these carry a 'Ref No' in the form 'MC-69-xxx' and may have been numbered from zero in each date year of issue. Serial number is missing on most of them. Brian.

For starters I'd like to thank everyone who has provided some feedback on what the issue might be. Since then I have double checked everything but I am somehow still having the issue. It seems that it will not shift once the cases are pressed together, even with the shift drum alignment bolt loose and not overtightened. Even with the bolts just snug, nothing more, it binds up and will not shift. Of course I'm am attempting to shift the gears by hand but I am constantly rotating the transmission as I shift through the gears so I don't think it's as simple as the gears not locking into each other. I am lost at this point Thoughts...?

Something similar has been reported before but the cause was never fully pinpointed, see here :-http://bridgestonemotorcycleparts.com/index.php?topic=4217.msg24418 A few long shots :- Could the crankcases be distorted ? This could happen if they have been bolted up with a knock pin not seated in the bearing recess, particularly the one that locates the smaller needle bearing on the gearbox output shaft. It's close to the shift dum. Any evidence of the knock pins being pushed down, cracked boss below ?

Are the bearing 'c' rings correctly located. The 3 thicker ones look very similar but one of them is slightly larger diameter and goes on the right side of the crankshaft. The other two fit the 6305N bearings for the gear box.

It has recently come to light (to me), via an article in the VJMC magazine, that the modern spec for the groove machined into Ntype bearing outer ring has changed since the late 60s when our bikes were built. The groove is now narrower and the BS 'C' ring will not fit, being too thick ( checked on some modern KOYO 6305N gearbox bearings, I've recently bought). Article referred to the 6205N bearing for a Kawasaki H1 clutch shaft. The thin outer rim of the modern bearing had been broken off by the old 'C' ring being forced into the groove when the cases were bolted together. This could distort the cases and jam the shift drum if modern 6305N bearing is used with original 'C' ring on a BS 350 engine. Something to be aware of and bear in mind. Brian.